Can a signal cross the Atlantic without a wire?

That time, that place

Maxwell predicted electromagnetic waves and Hertz produced them in the laboratory. Hertz himself said they would be of no use whatsoever.

In 1901 the only way across the Atlantic was submarine cable — hugely expensive to lay and maintain, and when it broke you sent a ship.

Why this question

Marconi attempted what physicists said could not work. Radio waves travel in straight lines and the Earth curves, so three thousand kilometres away is below the horizon.

On the arithmetic the signal could not arrive. He tried anyway.

What was found

In December 1901, at St John's in Newfoundland, he flew an antenna on a kite and received the Morse letter S sent from England. Three dots.

Why it worked came later: a layer high in the atmosphere, the ionosphere, reflects radio waves back down like a mirror. The Earth does curve — the signal bounced over.

He succeeded because of a layer he did not know about, and that layer was found because he succeeded. In 1912 the Titanic's distress call went out on this technology.